The toxicity of aldehydes and ketones, especially alpha, beta-ethylenically unsaturated aldehydes and ketones to biological waste treatment systems, even in low concentrations, has been recognized by those skilled in the art. A review article on this problem is presented by V. T. Stack, Jr. in Industrial and Engineering Chemistry, Volume 49 No. 5, page 913 (1957). Stack reports that of these compounds, acrolein has the most toxic effect on biological waste treatment processes. Wastewaters containing alpha, beta-ethylenically unsaturated aldehydes and ketones must be treated to reduce the concentration of these substances to very low levels before the waste water may be further treated by a biological system. Failure to adequately pretreat the wastewater streams results in the biomass being in danger of being killed or inhibited to a very low level of activity.
Treatment of waste streams containing alpha, beta-ethylenically unsaturated aldehydes and ketones are known in the art. U.S. Pat. No. 3,923,648 discloses a method for the disposal of such wastewaters comprising contacting them with sufficient base to render the pH of the wastewaters alkaline, maintaining the alkaline wastewaters at a temperature of about 25.degree. C. to 100.degree. C. for at least about 15 minutes and then degrading the wastewater in a biological system containing active biomass process rendering non-toxicity of alpha, beta-ethylenically unsaturated aldehydes and/or ketones to biological treatment systems by heating the wastewater with a slight excess of alkali at elevated temperatures. The preferred base is an alkali metal hydroxide, but the use of other bases is broadly disclosed including soluble organic amines such as methylamine, ethylamine, dimethylamine, triethylamine, and the like; and alkanolamines including monoalkanolamines, dialkanolamines, trialkanolamines, N-monoalkyl-monoalkanolamines, and N,N-dialkylalkanolamines and the like.
U.S. Pat. No. 5,459,229 discloses a process for the preparation of a 1,3-propanediol based polyester in which an aqueous acrolein-containing waste stream is treated with a sufficient quantity of base to increase the pH to above 7.5 for a time effective to lower the acrolein content, followed, optionally, by dilution and biotreatment. The base utilized is preferably an inorganic base, most preferably sodium hydroxide.
One objective of the present invention is to provide a more efficient and effective treatment to reduce the levels of alpha, beta-ethylenically unsaturated aldehydes and ketones in waste water streams.